The hock is a complex assembly of half a dozen bones, built to absorb shock as your horse brings his hind legs under himself and extend to propel him forward. It is an area that is subjected to a lot of stress, and it is easy for horses to get sore in the hocks, particularly if they are working hard or if there is a problem higher up in the back or in the feet.
Hock pain can also alter the horse’s movement, making it harder for them to move or even walk. Horses may take shorter strides on the sore leg, or they might shift more weight onto the front legs to get the pressure off the hock. In extreme cases, the pain might cause the horse to become hunched over.
Your vet can do a full lameness exam and take X-rays of the hock to see if there is an obvious problem. It is important to realize that sometimes the X-rays will show that a joint is sore, but it won’t necessarily be painful for your horse. This is because the X-rays show damage to the bone structure of the joint, but not necessarily any inflammation of the cartilage within the joint.
One of the most common injuries in the hock is a condition called distal tarsitis. This is a soft fluctuating swelling in the lower of the two hock joints, and it can be felt to enlarge when finger pressure is applied to the joint. This is a good sign that your horse’s hock is sore, but it won’t always be painful for your horse.
Other conditions that might cause a sore hock include idiopathic bog spavin, which usually presents with two soft and movable swellings on the back of the hock. This is not a serious problem in itself, but it can lead to problems up the back and in the SI (sacroiliac) joint.
Bog spavin is sometimes confused with capped or thoroughpin hocks, which are more serious issues that can block sound on a lameness exam and have a less favorable prognosis. It is also common for a horse with hock issues to develop muscle strain in the para-lumbar musculature of the spine from overcompensating for sore hocks.
Your veterinarian can do a joint injection of your horse’s hocks to put anti-inflammatory medication directly into the joint. This is typically done in a clinic setting under sedation and clipping, and the veterinarian will put a needle in the lower hock, or tarso-metatarsal, joint first. X-rays are taken to make sure that the injection is in the correct place and not in the upper, or distal intertarsal, joint. This will relieve the soreness, but it won’t solve the underlying problem and long-term use of this treatment is not recommended.